On average, the human scalp contains about 100,000 to 150,000 hairs. Each hair has three main stages of growth: anagen, catagen and telogen, after which the hair falls out. This hair growth cycle is repetitive and the duration of one cycle is different from other cycles, ranging approximately 3 to 6 years. Thus, the average adult normally loses about 50 to 100 hairs every day. In general, alopecia refers to a phenomenon wherein duration of the anagen growth phase is shortened and the percentage of hairs in the catagen and telogen phases increases, whereby the number of lost hairs is increased excessively and abnormally.
There are many theories to explain for loss of hair, including for example, poor blood circulation, excessive functioning of male sex hormone, excessive production and secretion of sebum, deterioration of scalp by peroxides, bacteria, etc., hereditary factors, aging, stress, etc. However, explicit mechanisms have not been revealed. Recently, the population suffering from hair loss is tending to increase, since changing dietary habits and stress imposed on individuals due to modern social environments, etc. has increased. Also, the age of the individuals affected by alopecia is dropping and furthermore, the population of female alopecia sufferers is rising.
One of preparations which are most commonly used for treatment and prevention of alopecia is one that contains minoxidil. There are two hair-regrowth agents which have received approval from the U.S. Food and Drug Administration, and minoxidil is one of those approved hair-regrowth agents. Minoxidil was originally developed as a hypertension drug for the purpose of reducing blood pressure. However, when using this drug, as a side effect, a trichogenous effect was observed and thereafter, this drug became famous as a hair-regrowth agent. Although mechanisms by which minoxidil works as a hair-regrowth agent is not clearly understood, it is inferred that minoxidil increases blood flow by expansion of blood vessels, whereby roots of hairs are supplied with more nutrition and eventually, growth of hairs are promoted.
Such a model of blood flow increase has been indirectly supported by a recent report that minoxidil enhances the expression of vascular endothelial growth factor (VEGF), a growth factor associated with vasodilatation in the dermal papilla which is a main cell making up the hair roots. Also, other than the vasodilative effect of the minoxidil in the hair-restoring mechanism, it has been reported that minoxidil promotes activation of dermal papilla cells in the roots of hair incubated in vitro, and growth of hair follicles in a tissue culture of follicles in vitro. These facts indicate that minoxidil may work directly on the roots of hair as a growth factor.
In addition, finasteride, a main component of Propecia which has started to be sold by Merck, is used for treatment of alopecia. It inhibits conversion of the male hormone testosterone into dihydrotestosterone, which is a more potent male hormone than testosterone. On December of 1997, the 1 mg finasteride tablet was approved by the US FDA as a hair-regrowth agent for treatment of male pattern hair loss in men only, and is now commercially available. In clinical studies, it has been demonstrated to have a significant trichogenous effect. However, there has been a report that finasteride may inhibit male sexual function as a side effect. Since neither finasteride nor minoxidil show superior effect in clinical tests, and there is concern about side effects, many researches are conducted to develop a new and improved hair-regrowth agents.
The cyclosporin family of drugs has immunosuppressive activity. It is also effective to inhibit growth of virus, fungus, protozoan, etc. and has various physiological effects such as nephrotoxicity, hepatotoxicity, hypertension, enlargement of periodontium, trichogenous effect, and so on, as side effects. Cyclosporin A, a representative cyclosporin, is a cyclic peptide having the following Chemical Formula, which comprises 11 amino acids, including several N-methyl amino acids and D-alanine at No. 8 residue. where MeBmt is N-methyl-(4R)-4-[(E)-2-butenyl]-4-methyl-L-threonine, Abu is L-α-aminobutyric acid, Sar is sarcosine, MeLeu is N-methyl-L-leucine,Val is L-valine, Ala is L-alanine, DAla is D-alanine, and MeVal is N-methyl-L-valine.
The amino acid form of cyclosporin A of the above Chemical Formula 1 is L-configuration, unless otherwise specified. The residue numbering of amino acids starts from MeBmt and proceeds clockwise, i.e. 1 for MeBmt and 11 for the last MeVal (N-methyl-L-valine) as shown in the Structure Formula 1. Nomenclature of various derivatives including cyclosporins A to Z, follows methods commonly used. For example, if Abu in the 2-position of cyclosporin A is substituted with L-alanine, L-threonine, L-valine or L-norvaline, the derivatives thus prepared are named cyclosporin B, cyclosporin C, cyclosporin D or cyclosporin G, respectively. Further, when the amino  acid residues of the cyclosporin derivatives differ from those of cyclosporin A, the derivatives are named by describing the substituent. For example, if sarcosine, being the amino acid residue 3 of cyclosporin A, is substituted with [D-2-ethylthio-sar3] or [D-2-propylthio-sar3], the derivatives thus prepared are named [D-2-ethylthio-sar3] cyclosporin A or [D-2-propylthio-sar3] cyclosporin A, respectively. Meanwhile, a common method for abbreviating amino acids is employed, that is, N-methyl-L-leucine is abbreviated by MeLeu, N-methyl-L-isoleucine by MeIle, N-methyl-L-Valine by MeVal, N-methyl-L-alanine by MeAla, N-methyl-L-norvaline by MeNva, L-leucine by Leu, L-isoleucine by Ile, sarcosine by Sar, L-serine by Ser, L-valine, Val, L-alanine by Ala, D-alanine by DAla, L-aminobutyric acid by Abu, L-threonine by Thr, and L-norvaline by Nva.
So far, possible development of cyclosporin as a hair-regrowth agent has been studied by many research groups. Particularly, researches involving animal hair regrowth tests, human alopecia areata, human male pattern alopecia, and inhibition effect of hair loss by chemotherapy in animal models have been widely conducted. In comparative experiments on mouse's back, it is shown that cyclosporin has a hair regrowth effect about 100 times superior to minoxidil Based on such findings, there have been attempts to utilize cyclosporin as a treatment for male pattern alopecia, and many applications for patents have been filed.
For example, Japanese Patent Publication Kokai Nos. Sho 60-243008, Sho 62-19512 and Sho 62-19513 disclose use of cyclosporin derivatives as a hair regrowth agent. Also, Europe Patent Publication No. 0414632B1 teaches a cyclosporin derivative modified in the 8-position, and PCT Publication No. 93/17039 teaches isocyclosporin. Moreover, U.S. Pat. No. 5,807,820 and British Patent No. 2,218,334A disclose cyclosporins with excellent transdermal absorption, pursuant to the use of cyclosporins as hair restorers.